The present invention relates to multiple-input multiple-output (MIMO) wireless communications and more particularly to MIMO wireless communications with full duplex radios.
Realization of the full duplex communication systems requires overcoming multiple implementation challenges. In particular it is very important to realize a system that can use full duplex communication without sacrificing the benefits of multiple antenna technologies. A practical system may address (1) how many antennas should be assigned for reception and transmission, respectively, (2) in OFDM (Orthogonal Frequency Division Multiplexing) systems how the assignment of the uplink and downlink should be performed, (3) in a single cell MIMO systems how the base station should schedule the uplink and downlink users and what should be the power split, and (4) finally in asynchronous single cell systems how should the MAC layer be designed to exploit the full potential of the full duplex access point as well as the full duplex clients.
Some prior works have considered the design of full duplex communication systems:    [1] M. Jain, J. Choi, T. Kim, D. Bharadia, S. Seth, K. Srinivasan, P. Levis, S. Katti, and P. Sinha, “Practical, real-time, full duplex wireless,” 2011.    [2] A. Sahai, G. Patel, and A. Sabharwal, “Pushing the limits of full-duplex: Design and real-time implementation,” Arxiv preprint arXiv:1107.0607, 2011.    [3] B. Radunovic, D. Gunawardena, A. Proutiere, N. Singh, V. Balan, and P. Key, “Efficiency and fairness in distributed wireless networks through self-interference cancellation and scheduling,” Tech. Rep. MSR-TR-2009-27, Microsoft Research, March 2009, http://research. microsoft. com/apps/pubs/default. aspx, Tech. Rep.    [4] S. Rangarajan, X. Zhang, S. Barghi, M. A. Khojastepour, and K. Sundaresan, “The case for antenna cancellation for scalable full-duplex wireless communications,” Tech. Rep. 2011-TR074, NEC Laboratories America, Inc., Tech. Rep.    [5] W. Pradeep Chathuranga, C. Marian, L. Matti, and E. Anthony, “On the effect of self-interference cancelation in multihop wireless networks,” EURASIP Journal on Wireless Communications and Networking, vol. 2010, 2010.
In [2] the authors estimate the channel and reconstruct the self-interference from digital samples. By using an extra transmit antennas the authors in [1] create a null at a single receive antenna. A digital noise cancellation algorithm known as active noise cancelation is used in [1]. The implementation of the active noise cancellation is performed through the use of QHx220 chip. In prior work [4], the authors have proposed the use of two copies of the self-interference signal in which case we need an extra Receive antenna for each original receive antennas.
In this specification, we address schemes and methods that address all the four problems described above. In particular, we provide guidelines on how to split the antennas between the transmit and receive RF (radio frequency) chains. We also provide method of allocating different tones in OFDM systems to uplink, downlink or full duplex (simultaneous uplink downlink) transmission. We also address the problem of user scheduling for full duplex communication in single cell. The full duplex scheduling is challenging due to the interferences that the uplink users will cause on the downlink users. The proposed scheduling algorithm depends on the number of transmit antennas and the number of active users and their channel gains. For a single cell systems when the scheduling is not possible and random access scheme is used, we also propose a method by which the base station or the access point can admit a new uplink communication while a downlink communication is in progress or it may initiate a new downlink transmission when an uplink transmission is already in session.